IOWA CITY, Iowa - Law enforcement officers across Iowa are getting better at catching both drunk and drugged drivers, according to Sgt. Paul Batcheller of the Iowa City police department. Over the past two years an estimated 500 officers have taken part in a specialized course focused on catching drivers under the influence of drugs or alcohol.

"It is a continuing change going on out there, with the prescription drugs and now the synthetic drugs," said Jim Meyerdirk, State Coordinator of the Drug Recognition Expert (DRE) program for the Governor's Traffic Safety Bureau. "The problems that we're experiencing, we have to train our officers."

Last week nearly 100 officers from Ames to Coralville participated in two separate Advanced Roadside Impaired Driving Enforcement courses. The program, established by the National Highway Traffic Safety Administration, is a bridge between basic academy training and the growing DRE program. The state hopes to offer the course to all officers across the state in the next several years.

As part of the training, officers spent about an hour administering field sobriety tests to volunteers who were legally drunk.

"Doing it in front of the mirror isn't the same as doing it with an actual drunk person, everything changes dramatically," said Adam Krack, an Iowa City police officer who participated in the training.

Volunteers drank in a monitored room at the Johnson County Joint Emergency Communications Center for about two hours prior to the training. Breath samples were taken to insure the volunteers surpassed the legal blood alcohol limit of 0.08. Testing with actual drinkers also helps officers spot drug use.

"If you have somebody out here that's failing these tests, but their blood alcohol doesn't match, there's usually a reason," said Batcheller, a certified DRE who helped lead the training.

A recent increase in drugged driving arrests in Iowa City show officers have become more conscious of drug impaired driving.

"It used to be, you were drunk or tired," said Meyerdirk. "If you didn't register [on a breathalyzer] you were on your way."

From 2011-12 officers in Iowa City charged 178 people with drugged driving. During the previous two-year span they charged 75 people for driving on drugs. In 2008 they made just 15 such arrests.

None of the volunteers, who were given a ride home by sober drivers after the training, passed all of the tests administered by officers.

"I think this puts it in perspective, if you drink at all don't drive," said Dale Handley, a 23-year-old volunteer from North Liberty. "Basically if there is any doubt in your mind, I don't think you should try [to drive]."

About half of the volunteers passed a series of walking tests, but failed an eye test. Intoxicated drivers almost always fail eye tests, Batcheller said. Officers train with alcohol instead of drugs because it is a gateway to detecting all impairment.

"If officers haven't gotten the alcohol part down yet, they're going to really struggle with the drug part," said Meyerdirk. There are many similarities between drunk driving and drugged driving, he said.

The alcohol was donated by Anheuser Busch in an effort to increase drunk driving awareness.